The present invention relates to a display device well adaptable for a document filing system in which picture information on a series of documents or the like is sequentially stored in a memory unit and, when desired, necessary picture information is retrieved and read out from the memory unit.
In a document filing system recently developed and practically used, an input device such as a photoelectric converter using laser beams converts the picture information on the document, and the picture information on the document into electrical signals, and the converted picture information is sequentially stored in a memory unit. When some picture information that has been stored is desired to be read out, the selected information is retrieved and displayed on a CRT screen of a display unit or printed out.
In storing the picture information in the document filing system, if a document is erroneously set upside down on the input device, the picture information is stored in this directional state. When such picture information is read out and printed out, the document picture is printed upside down on a paper. Since the printed paper may be turned upside down, this presents no practical problem. When the picture information is displayed upside down on the screen of the CRT display, the problem is serious.
In the case of a document of A4 size, for example, the picture information is normally printed out vertically standing, but drawings, tables and the like may be printed out in a horizontal state. In the latter case, the picture information displayed on the CRT screen is brought down and hard to see, and this is unpractical.